The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory captions and links exemplifying features within the Earth system. The community is invited to contribute digital imagery, short captions and relevant links.

Lunar Halo above Quebec

The photo above showing a conspicuous 22 degree lunar halo was captured from the Observatoire de la Découverte in Quebec, Canada on January 21, 2008. Randomly oriented, pencil-shaped ice crystals in cirrus clouds often produce 22 degree halos (angular distance of 22 degrees from the Sun or Moon). The darkened area within the halo is analogous to Alexander's dark band between the primary and secondary rainbow. In essence, light cannot be scattered into this region by simple refraction.